Extraction of hydrocarbon mixtures with hydroxy sulfones



United States Patent EXTRACTION 0F HYDROCARBON MIXTURES WITH HYDROXY SULFONES Thomas D. Nevitt, Crown Point, Ind., assignor to Standard Oil Company, Chicago, 11]., a corporation of Indiana No Drawing. Application April 21, 1955 Serial No. 503,026

11 Claims. (Cl. 260-674) This invention relates to a process for the partial or complete'resolution of hydrocarbon mixtures into their components by selective extraction thereof with novel liquid selective solvents. In' one particular aspect, this invention relates to the selective extraction of aromatic hydrocarbons from mixtures of aromatic and aliphatic hydrocarbons which are commercially produced as processed or unprocessed petroleum oils or mineral oils, coal tar oils, shale oils and the like. Various aromatic hydrocarbons are of value as solvents and for the preparation of resins, plasticizers and various other chemical derivatives; in addition, their removal from various hydrocarbon stocks containing the same may be desired in order to prepare partially dearomatized hydrocarbon stocks for thermal or catalytic cracking, for hydrogenation operations, for use as heater oils and for other purposes.

With the commercial development of new processes for producing aromatic hydrocarbons boiling within the gasoline boiling range by cyclization-dehydrogenation of parafiinic hydrocarbons and by the dehydrogenation of cycloalkanes there has come an increased demand for processes to separate and concentrate the aromatic hydrocarbons thus produced. Thus, with the commercial development of such processes as hydroforrning, platinum catalyst reforming of naphthas, and the like, a tremendous potential has been created for the production of nitrationgrade aromatics such as benzene, toluene and xylenes for use by both the petroleum and chemical industries.

It is an object of my invention to provide a process for the selective extraction of hydrocarbon mixtures with novel selective solvents. Another object of my invention is to provide the art of selective extraction of hydrocarbon mixtures with a class of novel solvents, viz. certain low molecular weight hydroxyalkyl alkyl sulfones. A further object of my invention is to provide for the employment of certain low molecular weight hydroxyalkyl alkyl sulfones in a process for the selective extraction of aromatic hydrocarbons from homogeneous liquid mixtures thereof with aliphatic hydrocarbons, particularly saturated hydrocarbons. A further object is to provide processes for the concentration and purification of aromatic hydrocarbons, particularly those containing not more than about carbon atoms per molecule. An additional object is to provide a process for the selective extraction of aromatic hydrocarbons from non-viscous neutral oils. Yet another object is to provide a process for the selective extraction of olefinic hydrocarbons from saturated hydrocarbons. A further object of this invention is to provide a process for the separation of closeboiling or azeotropic mixtures of hydrocarbons by selective extraction with certain liquid low molecular weight hydroxyalkyl alkyl sulfones. Another object is to provide a process for refining hydrocarbon oils by extraction with specified liquid low molecular weight hydroxyalkyl alkyl sulfones. These and other objects of my invention will become apparent from the ensuing description thereof.

Briefly, I have discovered that hydroxyalkyl alkyl sultones having the formula RSO CH (CH ),,OH, wherein 2,849,514 Patented Aug. 26, 1958 R is an alkyl group containing 1 to 3 carbon atoms, inclusive, and n is 1 to 2, inclusive, are excellent selective solvents for the purposes mentioned above. The sulfones conforming to the above general formula are thermally stable, high boiling liquids which are characterized by excellent selectivity for relatively polar molecules, including not only relatively polar hydrocarbon molecules but. also organic sulfur, nitrogen and oxygen compounds which are present as indigenous components of various petroleum fractions or in hydrocarbon synthesis products, for example products of the reduction of carbon monoxide in the presence of catalysts. From the manipulative standpoint, the novel solvents of the present invention are used in conventional fashion. Sufiicient solvent should be employed to maintain a distinct liquid phase in which the solvent is the predominant component. The solvents of the present invention may be employed in processes of liquid-liquid extraction, gas absorption, extractive distillation or azeotropic distillation.

In liquid-liquid extraction temperatures within the range of 20 to 150 C. are employed. When technically feasible, it is preferred to employ temperatures close to the ambient temperature. In general, the range of about 0 to about C. is preferred in liquid-liquid extraction. The proportion of solvent is usually selected within the range of about 0.5 to about 50 volumes and preferably from about 1 to about 20 volumes of solvent per volume of feed.

Sufficient pressure is maintained on the extraction or absorption system to ensure that a liquid, predominantly solvent phase is present at all times. Ordinarily, pressures within the range of about 0 to p. s. i. g. are sufficient to effect this object.

In extractive distillation processes the temperature is maintained between the dew point of the feed stock and about 240 C. and the solvent concentration between about 5 and 99 wt. percent. Conventional extractive distillation conditions and equipment can be employed.

In accordance with my invention, the hydrocarbon feed mixture is first contacted either as a liquid or vapor with a suitable proportion of the selected hydroxyalkyl alkyl sulfone in the liquid condition. The liquid extract phase thus produced is subjected to a suitable procedure for the recovery of the sulfone solvent and of the extracted material. Thus, the extract phase may be separated into its components by extraction with a parafiinic hydrocarbon having a boiling point which differs from that of the extracted materials, which displaces extracted materials from the liquid extract phase into a second liquid layer, from which they may be recovered by fractional distillation. The liquid extract phase may also be diluted with water which extracts the hydroxyalkyl alkyl sulfone solvent, leaving a supernatant liquid layer containing extracted materials. It is also possible in some cases to freeze the solvent selectively from the extract layer. When a liquid ratfinate layer is produced, the solvent can be removed therefrom by distillation or by washing with water or other solvents for the hydroxyalkyl alkyl sulfones. If the raflinate is a distillate, as in extractive distillations or azeotropic distillation processes, it can be recovered by condensation and aftertreatments such as are applied to liquid rafiinate layers.

Raffinate and extracted materials can be subjected to conventional aftertreatments such as re-extraction with the same or diiferent solvents, washing with acids or alkalies, contacting with adsorbent materials, water-washing to remove traces of solvents, redistillation, etc.

The sulfones of this invention may be employed singly or as mixtures of two or more. They may be employed in aqueous solution or in conjunction with various other diluents which will affect their solvent power for aro- 3 matics. Such diluents are partially or completely miscible with water, and generally contain hydroxy groups, although this is not a limitation. Such diluents may be eifective in modifying the solvency, while avoiding the corrosivity characteristic of water. Among the diluents or auxiliary solvents may be mentioned glycerol, ethylene glycol, diethylene glycol, pentaerythritol, and the like. Since the selected sulfone solvents are extremely stable and chemically inert materials, diluents having acidic or basic characteristics may also be employed. Examples of such materials are formic acid, lactic acid, ethanolamines such as mono-, bi-, and triethanolamine and the like. Other examples of diluents or auxiliary solvents which may be mentioned are methyl ethyl sulfone, dimethyl sulfone, diethyl sulfone, liquid sulfur dioxide, the sulfolanes, dimethyl sulfoxide, various nitriles such as acetonitrile, bis-Z-cyanoethyl ether and the like; ethers or glycol ethers, tetrahydrofuran and the like; ,8, [3'-oxydipropionitrile, l3, p-thiadipropionitrile and the like; halogenated hydrocarbon solvents; esters of monocarboxylic acids and dicarboxylic acids; neutral organic nitrogen compounds such as dimethyl formamide, dimethyl hydantoin and the like; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and the like; aldehydes for example furfuraldehyde, crotonaldehyde and the like; etc. Where a diluent or co-solvent such as I have described is used, I prefer to use from about 0.1 to about 20% by volume thereof based on the volume of sulfone solvent employed.

In addition to the co-solvents or diluents described above, antisolvents can also be used to aid in the extraction step. Suitable antisolvents such as saturated hydrocarbons, perfluorocarbons, perfluoroamines, perfluoroethers and the like may be used in proportions of about to about 100 volume percent of the feed stock treated, and may be added to the feed stock to be dearomatized or introduced directly into the extraction zone.

In the extraction, a small proportion of a suitable surface-active agent may be added to increase the efliiciency of the extraction equipment. Thus long chain esters of perfluoroalkyl alcohols or perfluoroalkyl acids, perfiuoroalkyl amides and amines, etc. may be employed, in suitable concentrations between about 0.0001 and about 1 weight percent, based on the weight of the solvent (note G. B. Blake et al. paper presented before the Division of Petroleum Chemistry of the American Chemical Society, September 1954, pp. 313 if).

The present invention can be carried out in batch, continuous or semi-continuous operating cycles, and in one or more actual or theoretical stages, employing contacting and separation equipment such as has heretofore been employed in the selective solvent refining of petroleum stocks. Various types of liquid-liquid extraction operations and suitable extraction equipment are described, for example, in Chemical Engineers Handbook (McGraw-Hill Publishing Co., Inc. N. Y., 1950), pp. 716 if. and 747 if. It should be understood that the specific equipment employed forms no part of the present invention and that any equipment adaptable for the purposes of contacting the solvent with the hydrocarbon charging stock and thereafter separating an extract phase from the refined charging stock can be employed for the purposes of the invention.

The following specific examples are oflered to illustrate the invention but not unnecessarily to delimit the same. In each example the feed stock was a mixture of equal volumes of toluene and n-heptane. The feed stock was contacted under batch liquid-liquid extraction conditions with an equal volume of solvent at 25 C.; liquid extract and raffinate layers were produced by settling and were separated by decantation. The distinct liquid layers were then analyzed and selectivity values, i. e. beta values, were calculated from the data. The beta value or separation factor indicated in the following table is the molar ratio of toluene to heptane in the extract layer divided by the molar ratio of these hydrocarbons in the raflinate layer and corresponds to alpha, the separation factor calculated in fractional distillation processes.

The solvents of my invention are particularly effective in extracting aromatics from saturated hydrocarbons, but they can be used in other separations as well, for instance, the separation of olefins from aromatics, naphthenes from aromatics, naphthenes or parafiins from diolefins or olefins. In short, they may be used for hydrocarbon type separation. These solvents may also be used in other separations as the extraction of sulfur or oxygen compounds'from aromatics, olefins, paraffins, or naphthenes. They may also be used for the separation of highly unsaturated fatty acid esters from the less saturated fatty acid esters.

Other'applications of the extraction process of my invention are in the selective extraction of normally gaseous olefins from their mixture with normally gaseous parafiins, for example the selective extraction of ethylene from gaseous hydrocarbon streams containing ethane and methane, hydrogen, etc., the selective extraction of propylene from propylene-containing gas streams and the like. My invention is likewise applicable to the selective extraction of acetylene from gas mixtures containing the sameand methane, hydrogen, ethane, ethylene, etc. By the employment of the extraction or absorption process of the present invention, it is possible to produce normally gaseous unsaturated hydrocarbons of high concentration or purity, which is deemed to be extremely desirable in the further treatment or chemical conversion of said hydrocarbons.

Having thus described my invention, what I claim is:

l. A process for the selective separation of a hydrocarbon from a mixture of hydrocarbons of diverse homologous series, which process comprises selectively extracting said mixture with a liquid solvent conforming to the formula RSO CH (CH ),,OH, wherein R is an alkyl group containing 1 to 3 carbon atoms, inclusive, and n is l to 2, inclusive.

2. A process for the selective extraction of an aromatic hydrocarbon from a mixture thereof with an aliphatic hydrocarbon, which process comprises contacting said hydrocarbon mixture with a liquid selective solvent in an amount sufficient at least to form a distinct liquid phase, and separating an extract phase comprising said solvent and said aromatic hydrocarbon, said solvent conforming to the formula RSO CH (CH ),,OH, wherein R is an alkyl group containing 1 to 3 carbon atoms, inclusive, and n is 1 to 2, inclusive.

3. The process of claim 2 wherein said solvent is 2- hydroxyethyl ethyl sulfone.

4. The process of claim 2 wherein said solvent is 2- hydroxyethyl n-propyl sulfone.

5. The process of claim 2 wherein said solvent is 2- hydroxye'thyl isopropyl sulfone.

. 6. A process for the selective extraction of an aromatic hydrocarbon from a hydrocarbon mixture thereof with an aliphatic, which process comprises contacting each volume of said hydrocarbon mixture in the liquid condition with between about 0.5 and about 50 volumes of a liquid selective solvent at a temperature between about 20 C. and about C., and separating a raifinate phase from an extract phase comprising said solvent and said aromatic hydrocarbon, said solvent conforming to the formula RSO CH (CH ),,OH, wherein R is an alkyl group containing 1 to 3 carbon atoms, inclusive, and n is 1 to 2, inclusive.

7. The process of claim 6 wherein said hydrocarbon mixture boils within the gasoline boiling range.

8. The process of claim 6 wherein said solvent is 2- hydroxyethyl ethyl sulfone.

9. The process of claim 6 wherein said solvent is 2- hydroxyethyl n-propyl sulfone.

10. The process of claim 6 wherein said solvent is 2- hydroxyethyl isopropyl sulfone.

11. A process for the selective extraction of an aromatic hydrocarbon from a hydrocarbon mixture comprising essentially monocyclic aromatic hydrocarbons containing not more than 10 carbon atoms per molecule and satu rated hydrocarbons, which process comprises contacting References Cited in the file of this patent UNITED STATES PATENTS Kurtz Mar. 17, 1936 Buis Aug. 28, 1945 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2,849,514 August 26, 1958 Thomas D.. Nevitt It is herebf; certified that error appears in the-printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 3, line 12, for "biread di column 4, line 67, strike out "hydrocarbon", second occurrence; line 68, after "aliphatic", and before the comma, insert hydrocarbon e Signed and sealed this 28th day of October 1958n (SEAL) Attest:

KARL Hu AXLINE ROBERT C. WATSON Attesting Officer Commissioner of Patents 

1. A PROCESS FOR THE SELECTIVE SEPARATION OF A HYDROCARBON FROM A MIXTURE OF HYDROCARBONS OF DIVERSE HOMOLOGOUS SERIES, WHICH PROCESS COMPRISES SELECTIVELY EXTRACTING SAID MIXTURE WITH A LIQUID SOLVENT CONFORMING TO THE FORMULA RSO2CH2NCH2)NOH, WHEREIN R IS AN ALKYL GROUP CONTAINING 1 TO 3 CARBON ATOMS, INCLUSIVE, AND N IS 1 TO 2, INCLUSIVE. 